1. Field of the Invention
This invention relates to an AC/DC power supply means adapted for use with portable products such as radios and tape recorders and, more particularly, to a power supply means requiring substantially reduced storage space within the product.
2. Description of the Prior Art
In consumer audio electronics products such as portable radios and tape recorders, it is often desirable to provide switchable power supply means for operating the product at the option of the user from either batteries contained within the product or an external source of 120 volt alternating current electric power. Typically, AC electric power is supplied by means of an electric power cord having terminal means on each end for coupling the external power outlet to the audio product. The coupling to the audio product is provided to permit removal of the external cord when it is desired to operate the product from the internal battery power source. In order to minimize the possibility of loss of the cord, it is typical to provide storage means within the product for receiving the cord when operation on battery power is desired. The various power supply components, including the batteries, the AC line cord, and the electrical apparatus for converting relatively high voltage alternating current supplied through the line cord to relatively low voltage direct current, require considerable space within the audio products. In some smaller products, the space required for the various power components can amount to as much as one-half of the total volume of the product.
In portable audio products, it is highly desirable to minimize the total size of the product, consistent with retention of desired product features and performance quality. To achieve this goal, storage space for the line cord is eliminated in some products. This approach is not altogether satisfactory in that it often results in either loss of the line cord or unavailability of the line cord when operation from an external power source is desired. Another approach to product size reduction is to combine the line cord and the power conversion apparatus into solely external means for supplying low voltage direct current to the product. Again, there is a risk that the external components will be either lost or otherwise unavailable when operation from an external power source is desired.